Bucket cover attachment

ABSTRACT

In a turbomachine having a turbine wheel including a rotor with a plurality of circumferentially mounted turbine buckets thereon; adjacent turbine buckets interconnected by a diagonal cover piece; a bucket cover attachment device which permits limited articulation of the buckets relative to one another as the turbine buckets twist and untwist.

United States Patent [1 1 Ouellette Dec. 11, 1973 BUCKET COVER ATTACHMENT [75] lnventor: Joseph H. Ouellette, Albany, NY.

[73] Assignee: General Electric Company,

Schenectady, NY.

[22] Filed: Oct. 1, 1971 [21] Appl. No.: 185,670

[52] US. Cl. 416/196 [51] Int. Cl. Fold 5/22 [58] Field of Search ..416/190,191,195, 416/196 [56] References Cited UNITED STATES PATENTS 937,006 10/1909 McKee 416/196 1,618,285 2/1927 Kasley 416/196 3,180,616 4/1965 Miller 416/196 3,302,925 2/1967 Musick 416/196 3,527,546 9/1970 Zeman 416/196 3,417,964 12/1968 Ortolano 416/220 X FOREIGN PATENTS OR APPLICATIONS 480,544 5/1953 Italy 416/196 272,378 3/1951 Switzerland 416/196 Primary Examiner-Everette A. Powell, Jr. Att0rneyWilliam C. Crutcher et al.

[57] ABSTRACT In a turbomachine having a turbine wheel including a rotor with a plurality of circumferentially mounted turbine buckets thereon; adjacent turbine buckets interconnected by a diagonal cover piece; a bucket cover attachment device which permits limited articulation of the buckets relative to one another as the turbine buckets twist and untwist.

3 Claims, 4 Drawing Figures 1 BUGKETJICOVERATTACHMENT BACKGROUND OF THE INVENTION This invention relatesin general to a turbine bucket wheel construetionand in particular to a bucket cover attachment devicewhich allows limitedarticulation between adjacent buckets during bucket twist and un twist.

In U. S. Pat. No.3,302,925 granted Feb. 7, 1967 to Victor S. Musick andassigned t the assignee of the present invention, a diagonal cover piece interconnectingadjacent turbinesbuckets is disclosed. In that patent,

the downstream trailing edge of one bucket is connected withthe upstream leading edge of an adjacent bucket by means ofa cover piece which is fixed at each end to a respective adjacent bucket. The cover piece has lugs formed at opposite endswhich are inserted through transverse holes in adjacent bucket tips and then mechanicallylfastened in compressive abutment by a peening operation. The effect of this type of connectionis to rigidly secure a bucket cover to the turbine buckets andobviate an upper tie wire.

In U. S.Pat. application Ser. No. 136,884 filed Apr. 23, 1971 in the names of Musick and Fontaine and assigned to the assignee of the present invention, an Articulated Sleeve for Turbine Bucket Lashing is disclosed. The design philosophy behind this invention is that a turbine wheel, inwhich limited play is allowed between buckets, is more adaptable to centrifugal, bending, torsionaland thermal stresses. Limited play allows fora certain relieving of stresses before the stresses need be applied to the structure. Thus, in the Musickand Fontaine application, there is a sleeve having clearance cuts at both ends interposed between lugs onopposing blade faces to connect turbine blades. In operation, theblades may twist or untwista certain amount before the blades become stressed. Thus, certain initial stressing is relieved by means of the rela- Itivelylimited play. allowed by the clearance cuts on the sleeve.

4 i It has been found desirable to incorporate this design philosophy into the device described in U. S. Pat. No.

vide a damping effect betweenbuckets while limiting blade twist andtuntwist.

Other objects andladvantages will become apparent from the following description of one embodiment of the inventionand the novel featureszwill be particularly pointed outhereinafter in the claims.

SUMMARY OF THE INVENTION F Ina turbine wheel. of the type having a plurality of circumferentiallyvmounted buckets, each bucket interconnected with anladjacentbucket by means of a diagonalbucketcovervpiece; a flanged or rolled projection fixed' to the coverupiece at one .end and threaded through a transverse hole in the bucket and thereafter partially flattened' wherebyIimitedplay is permitted between the cover piece and the bucket and also between adjacent buckets.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial side elevation of a turbine rotor of the kind having diagonal bucket covers and articulator sleeve tie wires;

FIG. 2 is a radially inward view of two buckets of the turbine rotor in FIG. 1;

FIG. 3 is a top elevation view of the bucket attachment device, the dotted lines showing the final assembled position of the device; and

FIG. 4 is a section IV-IV taken from FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION In FIG. 1, a turbine wheel 11 is generally depicted as having a rotor 13, and a plurality of circumferentially mounted buckets or blades 15. The buckets may be fastened to the turbine rotor by means of a dovetail connection 17 or any other similar means.

Approximately midway radially outwardly on the bucket there maybe an articulator sleeve tie wire connection 19 of the type described in U. S. Pat. application Ser. No. 136,884 previously referred to in this application. This type of connection, as previously described, allows some relative movement or articulation as the turbine buckets twist and untwist.

At the tips of .buckets 15 (see FIG. 2) are formed transverse holes 21 in the trailing portion of the tips and transverse holes 25 in the leading portion of the tips. The buckets 15 are modified at their tip portions such that the upstream and downstream bucket surfaces 27 and 29, respectively, at the bucket tips are substantially planar, parallel to each other, and perpendicular to a bucket tip surface 31.. Transverse holes 21 and 25 are substantially perpendicular to surfaces 27 and 29. Between the trailing portion of each bucket tip and the leading portion of the next following'bucket tip Cover piece 35 covers a substantial portion of the radial opening between buckets 15..

Cover piece 35 has lugs 39 and 41 projecting therefrom. Lugs 39 may be of the type which will securely fasten in compressive abutment the bucket to the cover piece by mechanical upset or peening. The lugs 41 in combination with the diagonal shroud cover 35 constitute the subject matter of this invention. It is possible to interchange the position of lugs 39 and 41 so that the peened lugs 39 are on the downstream side 29 of the buckets and the lugs 41 are on the upstream side 27 of the buckets.

Referring now to FIGS. 3 and 4, lugs 41 are formed as part of the diagonal cover piece 35 andextend through holes 25 in the buckets 15. The upper portion of each lug is formed with a tub recess 55 defining a peripheral wall 59. The peripheral wall is rolled in such a manner that a force applied against the peripheral wall will cause the wall to spread outwardly and to form an overhang 61 (indicated by the dotted portion) thereby loosely connecting the diagonal cover to the bucket.

As is apparent from FIG. 4, the bucket and bucket cover are loosely connected to each other. This is because the construction allows for a clearance A to be formed between the bucket surface and the overhang. When the turbine rotor is in use, this clearance allows limited play until the bucket surface contacts the overhang, at which time stresses are introduced into the turbine blades. The clearance and limited play may be adjusted according to the amount the peripheral walls are spread outwardly or according to the force applied in securing the lug.

OPERATION In the preferred embodiment of this invention the turbine wheel will usually be of the type having an articulator sleeve tie wire connection. As was earlier pointed out, the articulator sleeve allows some relative motion between buckets. As the turbine rotor changes speed, adjacent buckets will tend to twist or untwist causing a small variation in the distance between buckets which is accommodated by the clearance provided. The incorporation of the present invention into the diagonal bucket cover also permits articulation because of the limited play allowed by means of the loose connection afforded by projection 41. However, the articulation allowed by the articulator sleeve may be limited in this embodiment according to the tightness with which the projection 41 is secured.

While there is shown what is considered at presentto be the preferred embodiment of the invention, it is, of

mounted about a rotor, said turbine wheel having a plurality of circumferentially mounted turbine buckets extending radially outwardly therefrom; a bucket cover extending diagonally between adjacent bucket tips, said bucket tips formed with transverse holes therethrough communicating the upstream side of the bucket with the downstream side of the same bucket, at least one transverse hole formed in both the leading edge and the trailing edge of each bucket; and further comprising:

at least one lug extending from each end of said bucket cover through the transverse hole at the respective leading edge of one bucket and the trailing edge of an adjacent bucket;

at least one of said lugs formed with a tub recess defining a peripheral wall which is partially peened to form an overhang for partially abutting said bucket; and,

a clearance provided between said overhang and said bucket whereby a loose connection is formed permitting bucket twist and untwist.

2. The bucket cover recited in claim 1 wherein one of said lugs is securely fastened in compressive abutment to one bucket to provide a tight connection; and, the other lug is loosely fastened to an adjacent bucket whereby limited play is permitted between adjacent buckets to accommodate bucket twist and untwist.

3. The bucket cover recited in claim 1 wherein there are a pair of lugs extending from each end of said bucket cover said lugs, extending into a pair of transverse holes, respectively, in each leading edge of one bucket and the trailing edge of an adjacent bucket; and,

at least one pair of said lugs being loosely fastened to form a clearance between the ends of said lugs and the buckets whereby limited play is permitted between adjacent buckets to accommodate bucket twist and untwist. 

1. In a turbomachine including a turbine wheel mounted about a rotor, said turbine wheel having a plurality of circumferentially mounted turbine buckets extending radially outwardly therefrom; a bucket cover extending diagonally between adjacent bucket tips, said bucket tips formed with transverse holes therethrough communicating the upstream side of the bucket with the downstream side of the same bucket, at least one transverse hole formed in both the leading edge and the trailing edge of each bucket; and further comprising: at least one lug extending from each end of said bucket cover through the transverse hole at the respective leading edge of one bucket and the trailing edge of an adjacent bucket; at least one of said lugs formed with a tub recess defining a peripheral wall which is partially peened to form an overhang for partially abutting said bucket; and, a clearance provided between said overhang and said bucket whereby a loose connection is formed permitting bucket twist and untwist.
 2. The bucket cover recited in claim 1 wherein one of said lugs is securely fastened in compressive abutment to one bucket to provide a tight connection; and, the other lug is loosely fastened to an adjacent bucket whereby limited play is permitted between adjacent buckets to accommodate bucket twist and untwist.
 3. The bucket cover recited in claim 1 wherein there are a pair of lugs extending from each end of said bucket cover said lugs, extending into a pair of transverse holes, respectively, in each leading edge of one bucket and the trailing edge of an adjacent bucket; and, at least one pair of said lugs being loosely fastened to form a clearance between the ends of said lugs and the buckets whereby limited play is permitted between adjacent buckets to accommodate bucket twist and untwist. 